1. Field of the Invention
This invention relates generally to retractable coverings for architectural openings or the like that include a fixed head rail, a vertically moveable bottom rail and a vertically moveable middle rail with a shade material extending between the middle rail and the bottom rail. The shade material is flexible and retractable such that it can be extended between the middle rail and bottom rail or stacked in a retracted condition between the middle rail and the bottom rail. A control system is adapted to reciprocally move the middle rail independently of reciprocal movement of the bottom rail. The shade material can therefore be extended or retracted between the middle rail and the bottom rail and positionable between a retracted position adjacent to the head rail and extended positions displaced from the head rail.
2. Description of the Relevant Art
Coverings for architectural openings such as windows, doors, archways and the like, have taken numerous forms over many years. Early simple forms of such coverings amounted to fabric draped or otherwise suspended across an opening while in recent years more sophisticated coverings have been developed.
By way of example, Venetian blinds have become a popular form of covering for architectural openings wherein a plurality of vertically spaced horizontally extending slats are pivotably supported by cord ladders so that the slats can be pivoted or tilted about horizontal longitudinal axis to move the covering between open and closed positions or the slats can be gathered into a vertical stack adjacent to the top of the architectural opening in a retracted condition of the covering.
Other forms of retractable coverings utilize various shade materials that can be extended or retracted from a head rail of the covering to a bottom rail and in some instances, a middle rail is provided between the head rail and the bottom rail. In such coverings, the shade material extends between the middle rail and the bottom rail and both the middle rail and the bottom rail can be independently moved relative to the head rail to vary the extension, retraction or placement of the shade material relative to the architectural opening in which the covering is mounted.
Shade materials can be of numerous types including those of the type described in co-pending U.S. application Ser. No. 10/581,872 filed Jun. 5, 2006, which application is the Section 371 (c) filing of PCT International application No. PCT/US2004/043043 entitled Retractable Shade for Coverings for Architectural Openings filed Dec. 21, 2004 wherein a plurality of horizontally disposed arcuate vanes are suspended off the front and rear face of a flexible support structure that is suspended from the head rail. the vanes can be gathered in a retracted condition by raising a bottom rail toward the head rail. Of course, the reverse movement of the bottom rail causes the shade material to extend.
The coverings which include a middle rail independently moveable relative to the bottom rail and head rail are commonly referred to as top down/bottom up shades inasmuch as the top of the shade can be lowered by dropping the middle rail and the bottom of the shade can be raised by raising the bottom rail. The independent movability of the middle and bottom rails enables an operator to position the shade material at any location in the architectural opening and to any extended state and accordingly, these coverings have become very popular.
As will be appreciated, the control systems for raising and lowering a middle rail relative to a head rail and independently of a movable bottom rail can be fairly complicated, but in order to assure reliable and extended operation of such control systems, it is desirable to keep them simple, and accordingly, attempts in the art are continually being made to simplify and thereby improve control systems for top down/bottom up coverings. The present invention has been developed for this purpose.